Secondary batteries have been widely distributed for mobile terminals such as mobile phones and notebook computers and electric vehicles, and are repeatedly used through charging and discharging. In secondary batteries of the related art, electrodes were deteriorated from the repetitive charging and discharging of large power and large capacitance, and furthermore, the characteristics of the batteries were also degraded from deterioration over time, deterioration caused by the oxidization of electrodes, and the like, thereby hindering the extension of the service life.
Particularly, regarding the oxidization of electrodes, there is an essential problem depending on the charging principles of individual secondary batteries.
In a lithium battery, a metal oxide containing lithium is used as the positive electrode, on the other hand, a material capable of storing and releasing lithium such as carbon is used as the negative electrode, and the materials are impregnated with an electrolytic solution made up of a lithium salt capable of dissociating ions and an organic solvent capable of dissolving the lithium salt. As an electrode for the above-described lithium battery, a carbon electrode made of graphite powder improved for high performance and an increase in capacitance has been disclosed (for example, refer to PTL 1, 2 or the like).
In addition, there is another proposal that, in a non-aqueous electrolytic solution secondary battery provided with a negative electrode containing silicone as a negative electrode active material, a positive electrode containing a positive electrode active material and a non-aqueous electrolytic solution, an additive suppressing the oxidization of silicone during the operation of the battery is contained in the negative electrode or on the surface of the negative electrode, and a film-forming agent for forming a film on the surface of the negative electrode in the non-aqueous electrolytic solution is contained (for example, refer to PTL 3 or the like).
In addition, in a polymer electrolyte fuel battery, a cell in which a solid polymer film is interposed between separator pieces is used as a unit cell and a number of cells are stacked, and, since the separator pinching the solid polymer film is required to have favorable conductivity and low contact resistance, a graphite separator has thus far been used. However, since the graphite separator is brittle, instead of graphite, stainless steel is used as the separator, the surfaces of a steel sheet are coated with passivation films formed of an oxide or hydroxide of Cr, Mo, Fe or the like that is a component of stainless steel, and the anti-corrosion effect for the basic steel is obtained from the barrier effect of the passivation film (for example, refer to PTL 4, 5 or the like).
As described above, a variety of countermeasures have been proposed regarding the oxidization of electrodes in individual secondary batteries from the viewpoint of the principles of battery functions and structural aspects.